Chapman, Timothy

Clarke, Geoffrey L

2021-06-11

Cold subducted oceanic lithosphere may stall in the uppermost portions of the lower mantle (660–700 km depth) as a consequence of its slow thermal equilibration and the negative d<i>P/dT</i> of reactions forming ferropericlase and bridgmanite. Evaluations of slab buoyancy in the lower parts of the transition zone have mostly neglected the effects of dynamic <i>P–T</i> paths and the temperature-dependent expansion or contraction of stalled slabs. Forward predictions from mineral equilibria and thermal modeling posit slab residence at the base of the mantle transition zone for <i>c.</i> 150–160 Myr, dependent on geotherm and the depth of stagnation (between 660–700 km). Slab components can attain density thresholds following heating and phase transformations over distinct periods: Basaltic crust will become positively buoyant after <i>c.</i> 4 Myr whereas ultramafic components will become negatively buoyant after <i>c.</i> 150–160 Myr. Slab components may thus separate and independently transit or escape the transition zone under circumstances of equilibrated mineral assemblages. The 660 km seismic discontinuity presents a filter for the partial recycling of the upper oceanic lithosphere into the upper mantle.

Journal of Geophysical Research: Solid Earth, 126(6), p. 1-16

2169-9356

2169-9313

https://hdl.handle.net/1959.11/31260

Wiley-Blackwell Publishing, Inc

Delayed Growth of Ferropericlase and Bridgmanite Controls Slab Residence at the 660‐km Discontinuity

Journal Article

Publication